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Myofibrillar activation failure in McArdle's disease
R G Cooper1, M J Stokes, R H Edwards
1University Department of Medicine, University of Liverpool, U.K.
Journal of the Neurological Sciences
|October 1, 1989
Summary
McArdle's disease causes premature muscle fatigue due to myofibrillar activation failure, not just excitation issues. This study identifies key differences for diagnosing glycolytic disorders.
Area of Science:
- Neurology
- Muscle Physiology
- Biochemistry
Background:
- McArdle's disease is a glycogen storage disorder affecting muscle energy metabolism.
- Patients experience premature muscle fatigue and exercise intolerance.
- Understanding the underlying mechanisms is crucial for diagnosis and management.
Purpose of the Study:
- To investigate the contractile properties of the adductor pollicis muscle in McArdle's disease.
- To differentiate between excitation and activation failure in muscle fatigue.
- To explore potential diagnostic markers for glycolytic disorders.
Main Methods:
- Assessed muscle force and compound muscle action potentials during fatiguing contractions.
- Utilized supramaximal stimulation of the ulnar nerve at various frequencies.
- Compared contractile properties between normal volunteers and patients with myophosphorylase deficiency.
Main Results:
- Patients with McArdle's disease exhibited excessive force reductions across all tested frequencies.
- High-frequency contractions showed that myofibrillar activation failure, not excitation failure, contributed significantly to fatigue.
- Abnormal relaxation mechanisms were observed in patients.
Conclusions:
- Myofibrillar activation failure is a key factor in McArdle's disease fatigue, beyond excitation deficits.
- Findings support the role of metabolic product inhibition of ATPases.
- Identified objective differences can aid in screening for McArdle's disease and other glycolytic disorders.